The number of Monarch butterflies that reached wintering grounds in Mexico has rebounded 69 percent from last year's lowest-on-record levels, but their numbers remain very low, according to the World Wildlife Fund.

Last year, the Monarchs covered only 1.65 acres, the smallest area since record-keeping began in 1993. This year, the butterflies rebounded to cover 2.79 acres, according to a formal census by Mexican environmental authorities and scientists.

The orange-and-black butterflies are suffering from loss of milkweed habitat in the United States, illegal logging in Mexico and climate change. Each year, the butterflies make a migration from Canada to Mexico and find the same pine and fir forests to spend the winter, even though no butterfly lives to make the round trip.

"Of course it is good news that the forest area occupied by Monarchs this season increased," said Omar Vidal, head of the World Wildlife Fund in Mexico. "But let's be crystal clear ... it is still the second-smallest forest surface occupied by this butterfly in 22 years of monitoring."

At their peak in 1996, the Monarchs covered more than 44.5 acres in the mountains west of Mexico City.

Lincoln Brower, a leading entomologist at Sweet Briar College in Virginia, has said that with anything below 4.1 acres, "they will remain in the danger category and I will continue to be concerned." He said a population covering 9 to 12 acres would be a sign of significant recovery.

The butterfly population has plummeted before, and then partially recovered.

In 2001, driving rain and bitter cold killed millions, leading scientists to speculate that migrating populations would be seriously depleted in 2002. To their surprise, twice as many returned as some had predicted.

In 2004, unfavorable weather, pollution and deforestation caused a drastic decline in the population, but the next year, the butterflies bounced back.

The overall tendency since 1993 points to a steep, progressive decline. Each time the Monarchs rebound, they do so at lower levels. The species is found in many countries and is not in danger of extinction, but experts fear the migration could be disrupted if very few butterflies make the trip.

The temperate climate of the mountains west of Mexico City normally creates an ideal setting for the Monarchs. Every fall, tens of millions of the delicate creatures fly thousands of miles to their ancestral breeding grounds, creating clouds of butterflies. They clump together on trees, forming chandelier shapes of orange and black.

The migration is an inherited trait. No butterfly lives to make the full round trip, and it is unclear how they find the route back to the same patch of forest each year. Some scientists suggest the butterflies may release chemicals marking the migratory path and fear that if their numbers fall too low, the chemical traces will not be strong enough for others to follow.

Extreme cold and drought also hurt butterfly populations, and in Mexico, illegal logging can punch holes in the forest canopy that shelters them, creating a situation in which cold rainfall could kill millions.

Vidal said Mexico has been able to essentially stop illegal logging in the Monarch protected reserve, but he said habitat loss in the United States remains a huge problem. Milkweed, the butterflies' main source of food has been crowded out by pesticide-resistant crops.

"The question we should all be asking now" is whether the U.S. can halt the loss of milkweed habitat, he said.

Critical thinking challenge: Name four factors that have a negative impact on butterfly populations.

Pollution, deforestation, unfavorable weather, and the bitter cold played a factor in the negative impact on butterfly populations. the butterflies are beautiful creatures, they travel in large groups.

L.E 1999 blue

2/09/2015 - 08:59 a.m.

What I read was about butterfly. The article said that butterflies don't live to mack the trip around to go back to were they came from once the seasons change. Also the Monarch are suffering from milkweed from illegal climate change I'm Mexico. The Monarch butterflies have to travel from Canada to Mexico and they also find the same pine and forest to spend the winter.

TaylorHartman-Ste

2/09/2015 - 09:20 a.m.

I think that it is pretty cool that Monarchs are heavily populating our country. It is pretty neat to see different types of insects during the Spring season.

ratiaira

2/09/2015 - 01:50 p.m.

monarchs are really one of my favorite butterflies and I really want to see more of them they are so beautiful and orange and black my favorite colors so please let there be more of them

Ashleypatt

2/09/2015 - 01:57 p.m.

These butterflies are the most beautiful things out there. When i was little i use to catch these and then let them fly away. Its just about there colors that show true happiness. If there was more of these it will make the world more brighter and bring more happiness.

phoenix5

2/12/2015 - 09:46 a.m.

I fell that we should start planting milk weed and crack down on illegal logging so wee can keep that percentage up so they can live for years to come

NashMcComsey-Ste

2/12/2015 - 01:18 p.m.

Thank goodness for this article. The monarch butterfly migration is one of the things i remember from science class in elementary school, and it would be a shame if students in the future would not be able to learn about them.

zarid-Koc

2/15/2015 - 03:42 p.m.

I've noticed that more monarch butterflies are here in Las Vegas and Its different because there has never been so many. Monarch Butterflies are very pretty but I really hate the fact that they are getting killed and I looked up and found out that sometimes it's on purpose. People capture them and enjoy watching them die in small glass containers with little air holes. Butterflies are a beautiful part of nature and should be treated with respect just like us as human beings want to be treated.

9alexr

5/27/2015 - 12:44 p.m.

I just read the bee article which didn't seem to bee a good article. That article said that monarchs are going more endangered every year. But if this article is true that is amazing I always like to see monarchs and other pretty butterfly's flying around. The article stats that it was a better winter for them to survive and that they had safe migration to mexico and back.